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What is meconium?

The presence of meconium in your waters can signal health concerns for your new baby. What should you look for and what should you do?

What is meconium? The short answer is poo – your baby’s first poo, to be precise. It’s dark, sticky (think treacle), near impossible to wipe clean (don’t worry, later offerings are easier to deal with) and, mercifully, odourless. It’s also, unlike later poos, sterile. It’s made up of everything your baby has ingested while in the womb, such as mucus, amniotic fluid, water, lanugo (that downy hair babies have) and intestinal epithelial cells. For the majority of babies, it is simply the first poo (of many), and no cause for concern. It will simply result in a gooey first nappy.

When to worry In about five to 20 per cent of all births meconium is passed into the amniotic fluid. This is readily detected, as the normally clear amniotic fluid is tinged with green. If your waters break before you go into labour or when there’s no doctor or midwife around, do check that the fluid is clear and do tell your midwife immediately if it is not. If your baby inhales the meconium-stained fluid during delivery, or with his first breath, he may develop meconium aspiration syndrome (MAS). Other signs to watch out for include discoloration of the skin (if the meconium was passed a considerable amount of time before birth, this may be stained green); rapid or laboured breathing; slow heartbeat, or a low Apgar score. If aspiration is suspected, your doctor may use suction to clear as much fluid as possible from the lungs to ease breathing. As meconium is thick and sticky it may block the airways, thus lowering the efficiency of gas exchange in the lungs; the meconium-tainted fluid may also irritate and inflame the airways, possibly leading to chemical pneumonia. About a third of those infants who experience MAS require breathing assistance. In more serious cases your baby may need to spend time in the neonatal intensive care unit (NICU). Most babies with MAS improve within a few days or weeks, depending on the severity of the aspiration, and there is usually no severe permanent lung damage. There are studies, however, indicating that those born with MAS are at a higher risk of having reactive airway disease (lungs that are more sensitive and can possibly lead to an asthmatic condition).

Why does this happen? Frequently, fetal distress during labour causes intestinal contractions, as well as a relaxation of the anal sphincter, which allows meconium to contaminate the amniotic fluid. Additional risk factors include a difficult delivery; advanced gestational age; a mother who smokes cigarettes or who has diabetes, hypertension (high blood pressure), or chronic respiratory or cardiovascular disease; umbilical cord complications, and poor intrauterine growth.

What’s the risk factor? MAS develops in just five to ten per cent of cases where meconium has passed into the amniotic fluid (5-20 per cent of all births).

Did you know? Sometimes the meconium becomes thickened and congested in the ileum, a condition known as meconium ileus. Meconium ileus is often the first symptom of cystic fibrosis.

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